This invention relates in general to foam products and, more specifically, to methods of improving the flame resistance of foam products.
Foamed plastics have long been used in a variety of thermal insulation applications. Some, such as polystyrene, melt at moderately elevated temperatures so are used only at approximately room temperature or below, such as in insulation of coolers or refrigerators. Others, such as polyimides, have excellent resistance to high temperatures and may be used in high temperature applications. In cases where the insulation must resist direct exposure to flame, the insulation generally required cover layers of metal, asbestos or the like which are heavy and present other problems.
Metal oxides in the sub-micron size range are known to have excellent thermal insulating capabilities. However, because of the small particle size and the fact that particles of oxides such as aluminum oxide and silicon dioxide take strong particle electrical charges, these materials have been difficult to handle and employ in insulation. Generally, they have only been used when enclosed, typically in a reservoir-type enclosure. Furthermore, the oxides are rather transparent in the infra-red portion of the spectrum, compromising the otherwise good thermal insulating properties where large temperature differences exist across the particle mass.
Thus, there is a continuing need for improved insulation materials, resistant to high temperatures and flames.